Some interesting developments in memories:This Nanowerk story reports results out of Alex Zettl’s group at Berkeley on a memory cell that consists of an iron nanoparticle which can be moved back and forth in a nanotube. More information on this can be found at Zettl’s site here.

This memory, like someother nanotech schemes, relies on physically moving a small piece of matter to represent the state of the bit, and can thus be both very small, thus dense memory arrays, and highly stable. Whether it’s this particular approach or not, it seems likely that nanotech will get us memories that are both very dense and of archival-quality lifetime.

This Technology Review story describes a possible super-high-density material for optical storage like a CD or DVD. It consists of gold nanorods of various sizes suspended in a clear substrate. The nanorods act as tuned optical antennae (“nantennae”) which are addressed by converging laser pulses in such a way as to allow writing different bits at the same spot with different frequencies (colors, since it’s optical) and polarizations. Writing consists of focusing lasers so as to melt the nanorods in place, changing their properties enough to be detected by a read laser.

And finally, something that isn’t billed as nanotech but serves to demonstrate the fuzziness of the edges of the concept. This one is much closer to commercialization, as in 2011. It’s Unity Semiconductor’s CMOx memory, positioned as a replacement for flash. It’s the subject of this Information Week article. Like the Zettl memory, something physical is being moved: but it’s oxygen ions in a loose group:
The ions move back and forth between the conductive and insulating metal oxide layers, depending on voltage. (Go to this page for an animated slide show.) The memory is denser and faster to write than flash, the main question appears to be whether flash will catch up before 2011.